Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-08-07
2002-05-21
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S428000, C525S443000, C525S456000, C525S474000, C525S523000
Reexamination Certificate
active
06391969
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to powder slurry compositions and methods of using the same. The invention provides an improved powder slurry composition utilizing a first solid particulate component (a) comprising a carbamate or urea functional compound (i) which is dispersed in a crosslinking component (b) comprising at least one crosslinking resin (i) which is liquid at 20° C. More particularly, the powder slurry compositions of the invention utilize a crosslinking component (b) further comprising a self-crosslinking aminoplast resin (ii) and most preferably, a self-crosslinking aminoplast resin (ii) having at least two aminoplast groups and at least two groups which are reactable with said aminoplast groups but which are nonreactive with the particulate film forming resin.
BACKGROUND OF THE INVENTION
Powder slurry compositions have been used to provide a variety of advantages in the coating of articles. Powder slurry compositions typically include a first component that is in a solid particulate form and a second component that is liquid. The first component is dispersed in the second component to provide a slurry which can be applied using conventional spray application equipment and techniques.
Aqueous powder slurry compositions provide the advantages of powder coating compositions with the ease of application of traditional solvent borne coatings. As a result, powder slurry compositions have the potential for environmental and financial advantages.
However, powder slurry compositions do present performance and application challenges. Traditional powder slurry compositions typically utilize epoxy acid resin systems. Such systems often sacrifice scratch and mar resistance in order to obtain acceptable water resistance, chip resistance and etch resistance. The nature of the powder coating composition used in the powder slurry composition requires that temperatures above the T
g
of the powder resin be used followed by temperatures sufficient to affect crosslinking. Thus, high cure schedules are often required.
Application concerns typically require the use of powder slurry compositions having lower Tg resins. The use of lower Tg resins facilitates more rapid flow and improved appearance. However, storage and manufacturing problems can result when powder slurry compositions having lower T
g
resins are utilized. Manufacturing is particularly challenging, especially with acid epoxy resin systems. Separation, precipitation and/or agglomeration of the solid particulate component during storage may also be observed.
Inferior film adhesion and/or cracking of the applied powder slurry film during curing are sometimes observed. These negative performance characteristics can be magnified by higher film builds and storage stability.
Finally, finished films obtained from powder slurry compositions can exhibit lower gloss and/or inferior performance characteristics, particularly when balancing scratch and mar resistance against water resistance, chip resistance and etch resistance. It is often difficult to achieve an acceptable balance of properties among these characteristics, especially with traditional acid epoxy powder/powder slurry resin systems.
Thus, it is desirable to provide improved powder slurry compositions wherein the foregoing disadvantages are either eliminated or are minimized. Prior art attempts hereto have been unsuccessful.
SUMMARY OF THE INVENTION
The present invention provides a powder slurry composition comprising a powder coating composition comprising a first solid particulate component (a) dispersed in a crosslinking component (b) that must comprise at least one crosslinking resin which is liquid at 20° C. First component (a) is in solid particulate form having an average particle size of front 0.1 to 20 microns. It comprises a compound (i) having a T
g
>40° C. and at least one carbamate or urea functional group, or a group convertible to a carbamate or urea group appended thereto. Crosslinking component (b) comprises at least one crosslinking resin (i) which is liquid at 20° C. Most preferably, crosslinking component (b) will further comprise a self-crosslinking aminoplast resin (ii) having at least two aminoplast groups and at least two groups which are nonreactive with solid particulate first component (a) but which are reactive with said aminoplast groups. The powder slurry composition of the invention has a VOC of less than 1.0 lbs./gal and provides performance and application improvements over the prior art.
DETAILED DESCRIPTION OF THE INVENTION
The powder slurry composition of the invention requires two components, a first component (a) in solid particulate form having an average particle size of from 3 to 30 microns and a second crosslinking component (b). Second crosslinking component (b) must comprise at least one crosslinking resin (i) that is liquid at 20° C. so as to allow the dispersion of first component (a) therein.
First component (a) comprises a compound (i) having appended thereto at least one carbamate or urea functional group, or a group convertible to a carbamate or urea group. Compound (i) may be selected from the group consisting of oligomers and polymers having appended thereto more than one carbamate group or more than one urea group, or more than one group convertible to a carbamate or urea group.
Oligomers typically have a number average molecular weight of between 148 and 2000, a preferred number average molecular weight for the oligomers is between 460 and 1800 and a most preferred number average molecular weight is between 900 and 1300. Polymers typically have a number average molecular weight of between 2,000 and 20,000, with the preferred number average molecular weight for the polymers between 4000 and 6000. Mixtures of said oligomers and polymers may be used as compound (i). Number average molecular weight can be determined by the GPC method using a polystyrene standard. The carbamate or urea content of the polymer, on a number average molecular weight per equivalent of carbamate or urea functionality, will generally be between 120 and 1200, and preferably between 300 and 800.
Carbamate groups can generally be characterized by the formula:
wherein R is H or alkyl, preferably of 1 to 4 carbon atoms. Preferably, R is H or methyl, and more preferably R is H. Urea groups can generally be characterized by the formula:
wherein R′ and R″ each independently represent H or alkyl, preferably of 1 to 4 carbon atoms, or R′ and R″ may together form a heterocyclic ring structure (e.g. where R′ and R″ form for example, an ethylene bridge).
Groups that can be converted to carbamate include cyclic carbonate groups, epoxy groups, and unsaturated bonds. Cyclic carbonate groups can be converted to carbamate groups by reaction with ammonia or a primary amine, which ring-opens the cyclic carbonate to form a &bgr;-hydroxy carbamate. Epoxy groups can be converted to carbamate groups by first converting to a cyclic carbonate group by reaction with CO
2
. This can be done at any pressure from atmospheric up to supercritical CO
2
pressures, but is preferably under elevated pressure (e.g. 60-150 psi). The temperature for this reaction is preferably 60-150° C. Useful catalysts include any that activate an oxirane ring, such as tertiary amine or quaternary salts (e.g. tetramethyl ammonium bromide), combinations of complex organotin halides and alkyl phosphonium halides (e.g., ((CH)
3
SnI, BU
4
SnI, Bu
4
PI, and (CH
3
)
4
PI), potassium salts (e.g., K2CO
3
, KI), preferably in combination with crown ethers, tin octoate, calcium octoate, and the like. The cyclic carbonate group can then be converted to a carbamate group as described above. Any unsaturated bond can be converted to carbamate groups by first reacting with peroxide to convert to an epoxy group, then with CO
2
to form a cyclic carbonate, and then with ammonia or a primary amine to form the carbamate.
Oligomeric compounds useful as compound (i), and having more than one carbamate functional group, have the general formula:
wherein
Harris Paul J.
Ohrbom Walter H.
Rehfuss John W.
BASF Corporation
Golota Mary E.
Moore Margaret G.
LandOfFree
Powder slurry compositions with solid particulate carbamate... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Powder slurry compositions with solid particulate carbamate..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Powder slurry compositions with solid particulate carbamate... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2905376